The present invention relates generally to input devices for digital systems, and more particularly to a joystick that detects position and motion using a capacitive sensor.
Joysticks are well-known input devices for digital systems such as personal computers, games, hand-held personal organizers, and the like. They are particularly used by the gaming community for controlling the actions of characters or objects within a gaming environment. They are also used in industrial environments for controlling movement of objects or tools. Typically, a joystick may have a stickxe2x80x94usually mounted verticallyxe2x80x94for grasping by the user, and one or more buttons for performing various functions. The user moves the joystick in the direction he or she desires an action to occur, and the joystick senses the movement and translates it to signals to be interpreted by the system. In a variation of the joystick, the stick is a stationary microstick mounted on a device, and movement is determined by pressure on the stick in various directions.
Other types of input devices are also commonly used as pointing devices. For example, mice and trackballs have been widely used. An embodiment of these use a light source in conjunction with an optical sensor to determine movement. As the trackball or a ball located on the bottom of a mouse is rotated, encoder disks within the device rotate. The encoder disks have regularly spaced openings through which the light can shine through. By monitoring the light alternatingly turning on and off as the encoder disk rotates, the optical sensor detects the rotation. Movement can thereby be determined. Touchpads are another type of input device. A touchpad determinesxe2x80x94by various means such as resistive or capacitive sensingxe2x80x94the movement of a pointing device across its surface.
Many different mechanisms have been used in the past to detect movement of joysticks. One type of joystick uses potentiometers, with movement of the joystick moving a wiper on the potentiometer. Other types of joysticks have included optical, electromagnetic sensing such as Hall-effect sensors, and induction coils. For example, U.S. Pat. Nos. 4,685,678 and 4,855,704 describe induction coil joysticks. Another type of joystick is shown, for example, in U.S. Pat. Nos. 4,879,556 and 4,642,595. They show the use of a transmitter coil in the stick of the joystick, which is surrounded by receiving coils. Another type of design is shown in U.S. Pat. No. 4,654,576 which shows a metal disk attached to the stick with coils mounted on different sides of it. The metal disk has a tapered bottom, and if the joystick is tilted, the disk will come closer to certain coils, changing the inductance.
Joysticks that are currently known suffer from a variety of disadvantages. For example, they depend on mechanical parts that tend to deteriorate over time. They are also subject to variation due to mechanical tolerances. The wires and connections tend to wear out and eventually break with constant movement. In operation, these types of joysticks are not able to detect rotation of the handle and have no way of determining absolute position since they don""t have a reference point. Thus, only relative movement can be determined. Further, they often suffer from backlash where the cursor does not return to its original location when the joystick is moved to the opposite side and back to its original point.
The present invention combines a joystick with a capacitive touchpad for determining position and movement of the joystick. The joystick includes a stick mounted to allow movement, a conductive element at a first end of the stick, and a capacitive touchpad for sensing movement of the stick. The stick is, in effect, a virtual finger moving across the capacitive touchpad. Position and movement of the joystick is determinable by monitoring the capacitance on conductive traces in the capacitive touchpad. The capacitance of a particular conductive trace increases as the conductive element nears that particular conductive trace. A capacitive-type touchpad is advantageous in that it does not use mechanical parts that are subject to wear and deterioration over time. Moreover, the present invention allows for rotation of the stick and absolute positioning to be determined.
In one embodiment of the present invention, the capacitive touchpad is a hemispherically-shaped device. Because of the shape of the capacitive touchpad, as the conductive element moves, it remains equidistant from the capacitive sensor. In another embodiment of the present invention, the capacitive touchpad sensor is planar as in traditional touchpads. A spring may be mounted to the conductive element to allow movement with respect to the stick to keep the conductive element equidistant from the capacitive sensor.
In another embodiment of the present invention, the stick is split into two end sections with a conductive element at both end sections. The relative position of the two end sections may be determined by the capacitive touchpad and rotation of the stick determined therefrom.
In yet another embodiment of the present invention, the shape of the conductive element is used to determine rotation and movement of the joystick relative to a conductive trace. For example, the conductive element may be triangularly shaped. Thus, as the joystick is moved, the surface area of a particular conductive trace covered by the conductive element increases or decreases. By analyzing the change in capacitance, movement or rotation may be determined.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the attached drawings.